Spark-plug-terminal connection



July14, 1925.

. B. M. LUTZE SPARK PLUG TERMINAL CONNECTION Filed Jan. so. 1920 gar/ms. we? @btovmm d WMTSFM Patented uly 14, 1925.

UNITED STATES 1,545,565 PATENT OFFICE.

BURT M. LUTZE, or FLINT, MICHIGAN, ASSIGNOR To GENERAL MoToRs CORPORA- TIoN, or DETROIT, MICHIGAN, A CORPORATION or DELAWARE.

SPARK-PLUG-TERMINAL CONNECTION.

Application filed January 30, 1920. Serial No. 355,087.

use the same, reference being made therein to the accompanying drawings, which form a art of this specification.

1y invention relates to ignition systems for use with internal combustion engines, and the object thereof is to provide an improved connection or joint by the use of which the leading in conductors or cables may be more readilyv attached to and detached from the spark plugs of the igniting system of the engine than has heretofore commonly been the case.-

A further object of my invention is to provide a joint or connection for use in ignition systems and in which the leading in electrical conductors or cables may be at tached to and detached from the central electrode of the lug by imparting angular movement to t c said conductors about the central electrode of the plug as a pivot; and vwhich connection when made and in use will be of such a character that it will not become accidentally broken or the supply conductor disengaged from the plug, due to the vibration of the engine or to other causes.

With the above and other objects of invention in view, my invention consists in the improved terminal connection for use with spark plugs illustrated in the accompanying drawing and hereinafter described and claimed; and in such variations and modifications thereof, within the scope of the concluding claims, as will be obvious to those 1skilled in the art to which my invention re-' ates.

Referring now to the drawing wherein the preferred embodiment of my invention is illustrated: j

Figure 1 is a view showing an electric conductor attached to the central electrodeof a spark plug by means of my improved connTetion or joint, the elements being shown in p Figure 2 is a view showing the under side of the terminal with which the leading in conductor or cable is provided,'for the purpose of conveniently attaching said cable to and detaching it from the plug, the view being upon a largerscale than Figure 1.

Figure 3 is a view showing a spark plug and leading in conductor connected therewith through and by means of my improved terminal connection in side elevation.

Figure 4 is a view showing the elements whereby the leading cable is connected with the plug partly in section, and upon a larger scale than in Figure 3, the view for the most part being upon a longitudinal plane indicated by the line 4, 4, Figure 2.

Referring now to the drawing, the reference numeral 5 designates the external shell or casing of anordinary type of spark plug, 6 the main insulating member thereof made ordinarily of porcelain and held in place within the shell 5, and 7 the central electrode of the plug which extends through a passage provided in the insulator, all as is usual in spark plugs.

T e upper end of the electrode 7 which is obviously the outer end thereof when the plug is in use is provided with a threaded portion 8; the threads being shown as provided upon the exterior surface of. an upwardly extending portion or sleeve 9 of a nut 10 which is in threaded engagement with the upper end of the electrode, although it will be appreciated that the threaded portion or member at the upper end of the electrode may be provided otherwise than by the use of a nut which is separate and distinct from the electrode.

The reference numeral 11 designates the leading in conductor or cable through which electricity is supplied to the central electrode of the plug, such conductor being illustrated as in the form of a plurality of fine Wires stranded together and the conductor as a whole being covered by heavy insulation, ordinarily of rubber, as indicated by the reference numeral 12. a

The reference numeral 13 designates a terminal with which the stranded supply conductor 11 is connected, and. which terminal in effect forms a continuation of the electri: cal conductor provided by the wires; said terminal being illustrated as made from a thin sheet metal blankv having wings 14. turned over and made to grasp the sheath 15 of the wires 11, and having also projections which in a finished terminal provide lugs 16 which-embrace the nut 17 and hold the same in permanentl fixed relation with the terminal and witli the'leading in conductor; so that the nut in efiect forms an integral part of the terminal and of the conductor through which current is supplied to the plug.

I wish to here state, however, that the particular manner in which the terminal, which forms a continuation of the wires 11 and is in effect a part of the leading in electrical conductor through which current is supplied-to the plug is provided, is quite ims material; and that said terminal is not necessarily made from a blank shaped in the manner ereinbefore explained, together with a nut as an element separate and distinct from the casing formed by the blank and which encloses a nut, as in the embodiment of my invention illustrated and herein described.

In the form of my invention shown the neck portion formed by turning over certain portions of the blank referred .to to form the wings 14, extends into the exterior rubber insulation of the leading in conductor, to thereby provide a more efiective insulation of the end portion of the electrical suppl conductor.

he end portion of the electrical conductor through which current is supplied to the plug is provided with an opening, said openmg being in'the nut 17 of the terminal 13, which is in effect a art thereof, in the form of my invention ill iistrated. This opening is threaded to correspond with the threaded end portion 8 of the central electrode; so that the endrportion of the leading in conductor ma be screwed onto the upper end of the sai central electrode.

It will be appreciated-that the terminal above referred to forms in effect an integral or more strictly speaking a unitary portion of the leading in conductor, and that the terminal is in no way movable relative to or inde endentl of the end portion of the said con uctor. t therefore follows that the leading in conductor may be connected vwith and disconnected from the central electrode by rotating said conductor terminal about an -axis correspondingwith the axis of the central electrode, durin which angular movement the threads wit the opening of the terminal portion of the conductor and the threads at the upper end of the central electrode are made to engage with and disengage from one another; the threads in the two members aforesaid thus forming co:

and the wire or wires thereo being operating locking elements which, when in engagement, act to detaehably hold the end of the leading in conductor fixedly attached to the central electrode. 1

The terminal of the leadin in conductor thus in permanent and fixed relation wlth oneanother, because of the integral construction of the, parts, it follows that the parts of the leadingin conductor all move together in attaching the same to and detaching it from the central electrode, and, in order that the angular motion imparted to the conductor to effect this connection with and disconnection from the plug may be reduced to as small an extent as possible, a multiple thread is preferably provided upon the threaded end portion of the electrode, the individual threads of which are arranged at a large angle relative to a horizontal plane extending through the electrode; the steepness of the threads being such, in the embodiment of my invention illustrated, that angular movement throughout about 90 degrees will be sufficient to screw the terminal onto the threaded portion of the electrode and provide a connection between the two which will be secure and one which will not jar loose, due to the vibration of the engine, when the device is in use. It will be appreciated, however, that the steepness of the threads, their number, and other details of the locking elements provided by the threads upon the electrode and within the opening of the terminal of the leading in conductor, are matters of degree, and may be varied throughout wide limits without departing from my invention.

In ignition systems such as. are commonly used in: internal combustion engines the leading in conductors through which current is su plied in proper sequence to'the plugs of t e various cylinders lead from a suitable distributor, and are of considerable length, so that there is quite a little slack in the said conductors; the slack bein sufiicient to permit the individual con uctors to be rotated throughout angles sufiicient to accomplish their connection with and disconnection from the plugs without disturbing the connections of their other ends with the distributes; My improved connection on joint therefore provides for connecting the ends of the leading in conductors with the plugs by swinging the conductor terminals about thecentral electrodes of the plugs as pivots,.thereby providing an ignition system in which the said conductors may be readil disconnected from the plugs by swingin t eir terminals about the plugs, and as rea ily reconnected with the plugs by a similar process; in each case without disturbing the fixed connections between the other ends ofthe supply conductors and the distributor. The threads upon the central electrode and within the opening in the terminalof the leading in conductor are ordinarily so related as to provide a comparativel loose joint between the parts to thereby acilitate the attachment of the cables to the plugs without binding. Such looseness as may be resent, however, will in no way interfere with the assa e of the high tension current employe to the central electrode; and the vibration of the engine will tend to cause the terminals of the leading in conductors to move downward which movement will tighten the joint between the terminal and the threaded portion of the central electrode, thus providing a connection which tends to become tighter when in use, and one which will not jar loose nor become disconnected due to the vibration of the engine.

Havlng thus described and explained my invention I claim and desire to secure by Letters Patent:

1. In a device of the class described, an internally. threaded nut'adapted to be attached to the central electrode of a spark plug, said nut provided with an external thread of coarse pitch, a terminal for a conductor provided with an internal thread for engaging the external thread of said nut, substantially as shown and described.

2. In combination, a spark plug having a central electrode provided with a coarsely threaded portion at its outer end; a terminal having an opening which is internally threaded to corres 0nd with the threaded.

end portion of sai electrode; and an electrical conductor secured to said terminal, the end of said conductor and all elements comprising said terminal being fixed rela-.

tive to one another.

3. In combination, a spark plug having a central electrode; a nut upon the upper end of said electrode and which nut is provided with an upwardly extending exteriorily threaded portion; and a-unitary electrical conductor and terminal arranged in fixed relation with one another and having an opening which is internally threaded to cor- -'respond with the threaded portion of the nut aforesaid.

4. In combination, a spark plug having a central electrode; a nut upon the upper end of said electrode and which nut is provided with a plurality of external screw threads; and a unitary electrical conductor and terminal having an opening which is interiorly threaded to correspond with the exteriorly threaded portion of said nut.

5. In combination, a spark plug having a central electrode exteriorly and coarsely threaded at its upper end; an electrical conductor; and a terminal assembled with said conductor so as to move therewith, and which terminal is provided with an opening which is threaded interiorly to engage the threaded portion aforesaid of said central electrode, the end of said conductor and all elements comprising said terminal being fixed relatively to one another.

In testimony whereof I aflix my signature.

BURT M. LUTZE. 

